Various types of apparatus for rolling a spiral bale fom a windrow or swath of hay or straw have been devised over the years, beginning with Luebben et al U.S. Pat. No. 799,175, issued in 1905; which was followed by other Luebben patents; and later Harrer U.S. Pat. Nos. 2,424,821 was issued to Allis-Chalmers; and a Kolzing 2,581,542 was issued to International Harvester Company. Subsequently, Harrer U.S. Pat. Nos. 2,656,786 and 3,004,377 issued to Allis-Chalmers on improvements in the rotary baling mechanisms.
All of the above identified patents made relatively small bales in a baling chamber into which hay was fed by an inclined conveyor. More recently, there have been a number of developments directed toward rotary balers which roll spiral bales that may be from 5 feet to 10 feet in diameter. The first such balers in the United States have been based broadly upon the type of mechanism disclosed in Avery U.S. Pat. No. 3,110,145, which rolls a windrow into a spiral bale in contact with the ground, much like rolling up a carpet. Reference in this regard is also made to U.S. Pat. Nos. 3,751,890, and 3,797,215. In addition to the several types of balers which roll a bale in contact with the ground, a number of large bale rollers have recently been developed which roll a large bale in a chamber above the ground. Reference is here made, for example, to U.S. Pat. No. 3,722,197.
A problem which is generally common to the existing rotary balers is a tendency to roll a bale so dense that air is unable to penetrate the center of the bale for drying the hay and preventing spoilage. It has heretofore been thought that the most desirable bale is one which is very dense throughout; but we have now learned that a bale of uniform high density is less desirable than one which is somewhat loose in the middle and has a small amount of relatively high density material around the outside.